Distinct sources and targets of IL-10 during dendritic cell-driven Th1 and Th2 responses in vivo.

Dendritic cells (DC) can both initiate an immune response and dictate its character. Cytokines are critically involved in this process and, although interleukin (IL)-10 is known as a potent immunosuppressant, the impact of its release from DC remains unclear. Here, we transfer pathogen-conditioned murine DC in vivo and show that, while DC-derived IL-10 can act to limit Th1 development, it is not required for Th2 induction. In both Th2 and Th1 settings, however, IL-10 from cells other than the initiating DC dominates the regulation of the emerging effector cell populations. Surprisingly, the critical source of IL-10 in this process is neither T nor B cells. These data illustrate the distinct actions of IL-10 during differently polarised, pathogen-focussed, DC-driven immune responses in vivo.